raise error for scalar values

theano/tensor/basic.py

@@ -3222,17 +3222,21 @@ class Nonzero(gof.Op):
     """
     def make_node(self, a):
         a = as_tensor_variable(a)
+        if a.ndim == 0:
+            raise ValueError('Nonzero only supports non-scalar arrays.')
         output = [TensorType(dtype='int64', broadcastable=(False, False))()]
         return gof.Apply(self, [a], output)
 
     def perform(self, node, inp, out_):
         a = inp[0]
         out, = out_
+
         result_tuple = numpy.nonzero(a)
-        if len(result_tuple) > 0 and len(result_tuple[0]) > 0:
+        if len(result_tuple[0]) > 0:
             result = numpy.vstack(result_tuple)
         else:
             result = numpy.zeros((len(result_tuple), 0))
+
         out[0] = result.astype('int64')
 
     def grad(self, inp, grads):
@@ -3306,6 +3310,8 @@ def flatnonzero(a):
     nonzero : Return the indices of the non-zero elements of the input array.
     nonzero_values : Return the non-zero elements of the input array
     """
+    if a.ndim == 0:
+        raise ValueError('Nonzero only supports non-scalar arrays.')
     return nonzero(a.flatten(), return_matrix=True)[0]
 
 def nonzero_values(a):